This grant application represents continuing support for the study of factors regulating renal electrolyte excretion. The research projects focus upon the role of the renin-angiotensin-aldosterone system in health and disease with particular emphasis on the change in response pattern of the renin-angiotensin-aldosterone system to variations in sodium intake in hypertension and in normal subjects. Sensitive radioimmuno-assays for angiotensin I, angiotensin II and aldosterone have permitted a critical look at the metabolism of angiotensin. The studies have provided a means of measuring the turnover rate or metabolic half-life of angiotensin II. Studies also permit evaluation of the role of the converting enzyme in regulating the levels of angiotensin II. In addition studies on the control of aldosterone in the absence of functioning renin-angiotensin system are being continued.